Tinkling Springs Presbyterian Church show the following Baptism dates for children of John Frazier:
John Frazier, Baptism May 8, 1743;
Isabell Frazier, Baptism Nov 10, 1745;
Robert Frazier, Baptism August 17, 1747.

Samuel is the oldest child of John Frazier, likely born around 1739 and James was likely born around 1741, as it appears there was about 2 years between John & Isabella Frazier's children, based on the three Tinkiling Springs records.